The Intellisense feature of Visual Studio interactively guesses, and lists all the types, methods etc. as you go on typing. How does it work?

Intellisense works by using Reflection to examine metadata in compiled assemblies and referenced libraries. As you type, it analyzes the context and queries type information to suggest valid completions for members, methods, and properties. XML is used for documentation comments, but not for the autocompletion mechanism itself.